Sometimes the unexpected happens.

Take the case of the female praying mantis delivered to the Bohart Museum of Entomology, University of California, Davis, for an educational display. The Bohart, home of some eight million insect specimens, also has a live "petting zoo"-- which houses tarantulas, Madagascar hissing cockroaches, and walking sticks.

And now: a female praying mantis.

UC Davis entomology student Justin "Wade" Spencer begins feeding and caring for her.

One day he wonders if she is gravid (pregnant). So when another entomology student, Minsu Kang, brings in a male praying mantis, Spencer makes sure that the female receives an extra portion of roach nymphs because of the possibility--well, a little possibility--that the female might lop off his head.

Females do that, you know, often during or after mating. Sexual cannibalism. (See 2006 YouTube video that's drawn nearly 3 million hits.)

So Spencer feeds her more yummy roach nymphs. All is well.

Finally, it's time to meet. The male praying mantis climbs inside the habitat.

The male looks interested. He takes one step toward her. She doesn't move. He takes another step. No response. “Oh good,” thinks Spencer.

Then she responds. “Food! Food! Food!"  She promptly grabs him with her spiked forelegs and lops off his head. Then she devours him. All of him.

Well, almost. The owner of the male praying mantis returns.  "Where's my praying mantis?” Kang asks.

Wade holds up a wing and some frass.

Sometimes the unexpected happens.